How to model this in a flexible and nondestructive way?
Make the bracket shapes, and set up an armature to deform them. Maybe just make one bracket and use a mirror modifier to copy it after it’s been deformed. Next, make a heavily subdivided plane, and put it where it would be if it was over the bracket’s location but they weren’t there. Use the shrink wrap modifier on the plane, and I think there is a setting where you can tell it to only deform along a certain axis, and make sure it stays outside of the target mesh.